A backlight unit using a micro optical switch and a three-dimensional (3D) image display device are provided. The backlight unit includes a light source configured to irradiate light, a light guide plate configured to guide the irradiated light, an optical switch array including micro optical switches disposed above the light guide plate for each of cells of the backlight unit, and a lens array disposed above and corresponding to the optical switch array. Each of the micro optical switches includes a substrate, a first electrode layer disposed on the substrate and including first holes, and a second electrode layer spaced apart from the first electrode layer and including second holes not facing the first holes.